Abstract
Sinus histiocytosis with massive lymphadenopathy, or Rosai-Dorfman disease, is a rare, benign type of non-Langerhans cell histiocytosis. The radiological findings are often nonspecific, potentially mimicking malignancies. The diagnosis is ultimately made based on pathology, in which the lymph nodes are characterized by a dilated subcapsular sinus filled with histiocytes that can exhibit emperipolesis. Immunohistochemically, the histiocytes are variably CD68 positive and reliably negative for CD1a. The features of head and neck sinus histiocytosis with massive lymphadenopathy are exemplified in this radiology-pathology correlation sine qua non article.